Biodiversity or Biological Diversity a sum of all the
different species of animals, plants, fungi, and microbial organisms
living on Earth and the variety of habitats in which they live. Each
species is adapted to its unique niche in the environment, from the
peaks of mountains to the depths of deep-sea hydrothermal vents, and
from polar ice caps to tropical rain forests.According to the definition of the Convention on Biological
Diversity, biodiversity is the variability among living organisms
from all sources, including terrestrial, marine and other aquatic
ecosystems and the ecological complexes of which they are part; this
includes diversity within species, between species and of ecosystems.

Aquatic biodiversity can be defined as the variety of
life and the ecosystems that make up the freshwater, tidal, and
marine regions of the world and their interactions. Aquatic
biodiversity encompasses freshwater ecosystems, including lakes,
ponds, reservoirs, rivers, streams,
groundwater, and wetlands. It also consists of marine ecosystems,
including oceans, estuaries, salt marshes, seagrass beds, coral
reefs, kelp beds, and mangrove forests. Aquatic biodiversity includes
all unique species, their habitats and interaction between them. It
consists of phytoplankton, zooplankton, aquatic plants, insects,
fish, birds, mammals, and others.

Importance
of Aquatic Biodiversity

Aquatic biodiversity has enormous economic and aesthetic value and is
largely responsible for maintaining and supporting overall
environmental health. Humans have long depended on aquatic resources
for food, medicines, and materials as well as for recreational and
commercial purposes such as fishing and tourism. Aquatic organisms
also rely upon the great diversity of aquatic habitats and resources
for food, materials, and breeding grounds.

Factors including overexploitation of species, the
introduction of exotic species, pollution from urban, industrial, and
agricultural areas, as well as habitat loss and alteration through
damming and water diversion all contribute to the declining levels of
aquatic biodiversity in both freshwater and
marine environments. As a result, valuable aquatic resources are
becoming increasingly susceptible to both natural and artificial
environmental changes. Thus, conservation strategies to protect and
conserve aquatic life are necessary to maintain the balance of nature
and support the availability of resources for future generations.

Threats
to Aquatic Biodiversity

Human activities are causing species to disappear at
an alarming rate. Aquatic species are at a higher risk of extinction
than mammals and birds. Losses of this magnitude impact the entire
ecosystem, depriving valuable resources used to provide food,
medicines, and industrial materials to human beings. Runoff from
agricultural and urban areas, the invasion of exotic species, and the
creation of dams and water diversion have been identified as the
greatest challenges to freshwater environments (Allan and Flecker
1993; Scientific American 1997). Overexploitation
of aquatic organisms for various purposes is the greatest threat to
marine environments, thus the need for sustainable exploitation has
been identified by the Environmental Defense Fund as the key priority
in preserving marine biodiversity. Other threats to aquatic
biodiversity include urban development and resource-based industries,
such as mining and forestry that destroy or reduce natural habitats.
In addition, air and water pollution, sedimentation and erosion, and
climate change also pose threats to aquatic biodiversity.

Overexploitation of species —Overexploitation of species affects the
loss of genetic diversity and the loss in the relative species
abundance of both individual and /or groups of interacting species.
The population size gets reduced because of disturbances in age
structure and sex composition. Efficient gears remove quick growing
larger individuals . consequently, the proportion of slow growing
ones increases and the average size of individuals in a population
decreases. Over-fishing causes change in the genetic structure of
fish populations due to loss of some alleles. Thus, genetic
diversity gets reduced .

Habitat modification —
Physical modification of habitat may lead to species extinction.
This is mainly caused due to damming, deforestation, diversion of
water for irrigation and conversion of marshy land and small water
bodies for other purposes. Construction of dams on river impedes
upstream migration of fishes and displaces populations from their
normal spawning grounds and separate the popultion in two smaller
groups. Deforestation leads to catchment area degradation due to
soil erosion which results into sedimentation and siltation. This
not only affect the breeding ground of aquatic organisms but cause
gill clogging of small fishes also.

Pollution load —Four forms of pollutants can be
distinguished-

Poisonous
pollutants — Agrochemicals, metals , acids
and phenol cause mortality, if present in a high concentration and
affect the reproductive functionality of fish (Kime, 1995).

Suspended
solids — it affects the respiratory
processes and secration of protective mucus making the fish
susceptible to infection of various pathogens.

Thermal pollution —
It cause increase in ambient temperature and reduce dissolved oxygen
concentration leading to death of some sensitive species.

These factors affect the aquatic biodiversity directly or indirectly.
Excessive mortality of organisms due to any of these factors may lead
to two type of effects – i) extinction of the species / populations
ii) reduction of population size.

Conservation
Approaches

Aquatic conservation strategies support sustainable development by
protecting biological resources in ways that will preserve habitats
and ecosystems. In order for biodiversity conservation to be
effective, management measures must be broad based.

Aquatic areas that have been damaged or suffered
habitat loss or degradation can be restored. Even species
populations that have suffered a decline can be targeted for
restoration (e.g., Pacific Northwest salmon populations).

An aquatic bio- reserve is a defined space within a water body in
which fishing is banned or other restrictions are placed in an
effort to protect plants, animals, and habitats, ultimately
conserving biodiversity. These bio-reserves can also be used for
educational purposes, recreation, and tourism as well as potentially
increasing fisheries yields by enhancing the declining fish
populations. These bio-reserves are also very similar to marine
protected areas, fishery reserves, sanctuaries, and parks.

Bioregional
management is a total ecosystem strategy, which regulates factors
affecting aquatic biodiversity by balancing conservation, economic,
and social needs within an area. This
consists of both small-scale biosphere reserves and larger reserves.

Watershed
management is an important approach towards aquatic
diversity conservation. Rivers and streams, regardless of their
condition, often go unprotected since they often pass through more
than one political jurisdiction, making it difficult to enforce
conservation and management of resources. However, in recent years,
the protection of lakes and small portions of watersheds organized
by local watershed groups has helped this situation.

Plantation
of trees in the catchment area of water body
prevent soil erosion and subsequently reduce the problem of
slitation in water body resulting in better survival of aquatic
organisms.

Avoid the establishment of industeries, chemical plants and thermal
power plants near the water resources as their discharge affect the
ecology of water body resulted in loss of biodiversity.

The
World Resources Institute documents that the designation of a
particular species as threatened or endangered has historically been
the primary method of protecting the
biodiversity.

Many specialized programs should be instituted to protect
biodiversity. For example, the USDA Forest Service started a
cooperative state-federal program with a goal to restore the health
of riverine systems and associated species.

Regulatory measures must be taken on wastewater discharge in the
water body to conserve biological diversity.

Increasing public awareness is one of the most important ways to
conserve aquatic biodiversity. This can be accomplished through
educational programs, incentive programs, and volunteer monitoring
programs.

Various organizations and conferences that research biodiversity and
associated conservation strategies help to identify areas of future
research, analyze current trends in aquatic biodiversity.